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VY. A Y WM Mm H H. E. WHITE MAGNETIC THERMAL RELAY Filed-Jan. 27, 1925 fi l 1 .36 34 32 29 Z8 a/ as wlNx-:ssss:

Patented July 3, 1928.

UNITED STATES PATENT OFFICE.`

HAROLD E. WHITE, OF WILKINSBURG, PENNSYLVANIA, ASSIGNOR T WESTINGHOUSEELECTRIC & MANUFACTURING COMPANY, A CORPORATION 0F PENNSYLVANIA.

MAGNETIC THERMAL RELAY.

Application led January 27, 1925.

My invention relates to electrical protective devices and particularlyto thermal relays.

One object of my invention is to provide a thermal relay that shall haverelatively few parts and that shall be easily and quickly assembled.

Another object of my invention is to provide a thermal relay that shallembody mag- Iletic means for permitting of easily and quickly varyingthe time of the operation thereof. i

In practicing my invention, I provide an electromagnetic switch having acore member that normally operatively engages a normally magneticcurrent-conducting member that is of variable area in lateralcross-section. By moving the current-conducting member laterally of thecore, the amount of material thereof that is subjected to the action ofthe magnetic eld of the core member is varied. i

In a modified form of device, the current conducting member is ofhelical spring form and the distance between the adjacent turns thereofmay be varied to vary the amount of material of the current-conductingmember subjected to the action of the magnetic Afield of the core andthe current conducting member.

In the single sheet of drawings,

Figure 1 is a view, partially in front elevation and partially insection, of a device embodying my invention with its associatedelectrical supply and control circuits` Fig. 2 is a view partially infront eleva# tion and partially in section, of a device embodying myinvention, a modified form of current conducting member being employedwith associated supply and control circuits, and v Fig. 3 is a sectionalview of a portion of the device shown in Fig. 2.

Referring more particularly to Fig. 1 of the drawing, 'a thermal relay11 comprises a supporting plate 12 of electric-insulating material uponwhich is mounted a winding 13 that may be covered by electric-insulatingmaterial 14 to protect the winding. A magnetizable core member 15 ismounted within the winding 13 and has vertical movement relativelythereto.

A rod 16 is secured to the upper end of the core member 15 and the upperendthere- Serial No. 5,064.

of moves in a bearing member 17 that is mounted on the front surface ofthe plate 12. A plurality .of collar members 18 and 1 9 are mounted onthe rod 16 in spaced relation relatively to each other and a collarmember 21 is loosely mounted on the rod 16 intermediate the members 18and 19.

Springs 22 and 23 are mounted on the rod 1 and extend between thecollars 18 and 21 and 21 and 19, respectively, in order to provide aresilient mounting for the collar 21, and a contact bridging member 24that is secured to the collar 21. The contact bridging member 24 isadapted to engage fixed terminal posts 25 and 26 that are mounted on thefront surface of the plate 12.

A current conducting member 27 is adjustably mounted on the frontsurface of the plate 12 above the lower edge thereof and in position tobe normally operatively engaged by the magnetizable core member 15. Themember 27 may be constituted by a bar of square or ot' rectangular shapein lateral section depending uponthe amount of cur? rent which it is tocarry.

The bar 27 is'provided with an angular recess 28 at one of its sides,which recess is so located as to be on the side away from the coremember 15. The eleet of the recess is to vary the areatraversed by thecurrent for a portion of the length of the member 27. Two bearingmembers 29 and 31 are provided to hold the member 27 in its properoperative position laterally thereof and the form and construction ofthese bearing members may be of any suitable ordesired type effectivefor the purpose desired.

The member 27 is provided with a pair of longitudinally-extending slots32 and 33 therein through which extend fixed studs 34e and 35. The studs31 and 35 are fixed in the plate 12 and nuts 36 and 37 are locatedthereon against the outer surface of the member 27 whereby'the member 27may be securely clamped against the plate 12 to prevent movement thereoflongitudinally and whereby, further, the position of the member 27laterally of the core member 15 may be varied as will be hereinafter-set forth in detail.

, The member 27 is made of a suitable normally magnetic material, suchas invar steel, which is an allo of iron and nickel and has the propertyo losing its magnetism at a predetermined elevated temperature. Suchmaterial is usually said to be magnetically reversible.

An energy translating device 38, here represented as a motor, or whichmay be constituted by a generator, a transformer or an electric heatingelement is adapted to be energized from a pair of supply circuitconductors 39 and 41 through a circuit breaker 42 which is hereillustrated as of the electromagnetic type in order to permit of itbeing suitably controlled by the thermal relay 11.

The circuit breaker 42 comprises, besides the usual lixed and movablecontact members, a holding coil 48, a core member 44 energized therebyand connected to the movable contact members, together with a springmember 45, that is adapted to open the cirf,

cuit when the winding 43 has been de-energized. The winding 43 isconnected in lseries circuit relation to the contact members 25 and 26and the contact bridging member 24 and across the supply circuitconductors 39 and 41.

The Winding 13 is here illustrated as comprising a relatively largenumber o'f turns of high resistance wire in order to permit of its beingconnected across the supply circuit conductors 39 and 41, as byconductors 46 and 47.

Referring more particularly to Fig. 2 of the drawings, a modified formof current conducting member is there illustrated in combination withother partsof a thermal relay, such as has been described in connectionwith Fig. 1 of the drawings.

A thermal relay 48, differing only from the relay 11 in the constructionand mounting of a current conducting member 49, here shown as ahelically wound strip, rod, bar or Wire of invar'steel. One end of themember 49 is connected to a short stud 51 that projects through anopening in a supporting member 52, of substantially L-shape, that issecured against the front surfaceof the plate 12 by means of a stud 53and a nut 54. A nut 55 is provided on the member 51 ateach side of thesupport 52, to hold it in proper operative position relatively to thesupport. The other end of the member 49 is connected to an exteriorlythreaded stud 5'6 that extends through an opening 57 in a bearing andsupporting member 58, of substantially L-shape. The member 58 is securedagainst the surface of the plate 12 by a bolt or stud 59 and a nut 61.An adjusting nut 62 is located on the outer end of the member '56 andsuitable provision is made to prevent a turning movement of the rodmember 5 6 relatively to its support 58 as by a-slot or groove 63extending longitudinally of the member 56, that has an integral vportionof the member 58, extending thereinto.

Referring more particularly to the construction illustrated in Fig. 1 ofthe drawing, the current traversing the Venergy translating device 38traverses also the current conducting member 27 and the lateraldimensions of the current conducting member are selected in accordancewith the value of this current. lt is evident that if a relatively heavycurrent be caused to traverse the member 27 for a sutlicient length oftime, the member 27 will be heated and the temperature of that portionthereof that is of reduced section by reason of the-recess 28, will beheated to a higher'temperature than the other portionsthereof and themagnetic properties thereof Will be lost at a predetermined temperaturedepending upon the com-` positionof the material, in a manner well knownin the art. It is further evident that that portion of thecurrent-conducting member that has the least area in cross-section, willreach this critical temperature before the other parts, thereof. y l

During the normal operation of the device, When the parts are in thepositions illustrated in F ig. l of the drawings, the Winding 13 isenergized and tends to move the core member 15 upwardly and away fromthe normally magnetic current-conducting member 27, but such movement isprevented by reason of the fact 'that the member 27 acts as an armatureor keeper for the core member and restrains it from any upward movement,or in other Words, the member 15 and the member 27 are differentiallyassociated.

The member 27 is heated not only by the current traversing the same, butalso by the eddy currents generated therein, caused by the alternatingcurrent flux traversing the same and the core member 15 in casealternating current is employed. However, the current-conducting memberis heated only by the current traversing the same, Where direct current.is employed.

If it be assumed that the current conducting member 27 has been moved tothe left, so that the minimum area of cross-section of the member isbelow the core member 15`and in contact therewith, and if this portionis heated to such temperature as to lose its magnetic properties, it isevident that the core lmember 15 will be moved upwardly-through theaction of field generated by the current traversing the winding 13,`whereby the contact bridging member 24 is disengaged from thecontactmembers 25 and 26 and the circuit through t-he holding coil 43 ofthe breaker 42 is interrupted. This permits the spring 45 to function tomove the contact arms to the right and to interrupt the circuit throughthe energy translating device 38 and through the current conductingmember 27.

When the current has been interrupted for a suiicient length of time topermit of the member 27 cooling tosuch temperature as will restore itsnormal magnetic property,

the core member 15 Will be again attracted towards the currentconducting member and caused to operatively engage the same whereby acircuit is again established through the holding coil'43 and the energytranslating deviceis again energized. i

The springs 22 and 23 serve to cushion the engagement of the contactbridging member with the contact members, thereby insuring a longer lifeof the device. Y

It' it is desired to employ a thermal relay of the type disclosed inFig. 1, to control the energization of the energytranslating devicehaving a high currentl rate, it is only neces sary to move the member27'. in such direction that a larger amount of magnetic material isdirectly under the core 15, whereby, as hereinbefore stated, thetemperature at which that portion of the current-conducting member 27,subjected directly to the influence of the magnetic field of the coremember, is increased. 4

A greater current is necessary or the same current must traverse thecurrent-conducting member for a longer period of time in order to resultin that portion of the current-com ducting member operatively engaged bythe.

core member reaching a suliiciently high temperature to becomenon-magnetic to permitv the core member to be released therefrom.

Referring to Fig. 2, the method of varying the amount of materialdirectly subjected to the influence of the magnetic field traversing thecore member 15 and the current conducting member 49, differs slightlyfrom that de scribed in that it is only necessary to increase thedistance between the adjacent turns of the member 49 to reduce theamount of ma- 'terial that is subjected to the action of the magneticield traversing the core member 15.

This action not only reduces the 'amountA of material that is subjectedto magnetic action,but also increases the ventilation, and both of theseaiect the value of the current at which the core member 15 will bedisengaged from the current conducting member 49. A barrier 64 may beprovided immediately below the current conducting member 49 and the coremember 15, which may also be varied as to its position and as to itswidth in order to permit of calibrating the thermal relay for a range ofcurrent values or for adjusting the same for this range of currentvalues, as may be desired in connection with the use of such thermalrelays with energy translating devices of different eapacities.

The device embodying my invention thus provides a relatively simpleelectromagnetic switch device dependent for its action upon the loss ofmagnetic properties of a normally magnetic current conducting memberthat may be adjusted to vary the exact value of the current at which thedevice will operate vor the time required for the device to oper-Various modilications and changes .may-

be made without departing from the spirit and scope of the invention,and I desire therefore that only such limitations shall be placedthereon as are imposed by the prior art.

I claim as my invention:

1. A thermal relay comprising an energizing winding, a magnetizable coremember therefor, contact members controlled by the movement of said coremember, a normally magnetic member, and means for permittin of varyingthe amount of material of said normally magnetic member that issubjected to the action of the magnetic lield of said core member andWinding.

2. A thermal relay comprising an energizing winding, a magnetizable coremember therefor, contact members controlled by the movement of said coremember, a normally magnetic, current-conducting member operativelyengaged by said core member, and means for varying the ratio of area of'that portion of the current-path directly subjected to the influence ofthe magnetic' field of the core member to the radiating surface thereof.

3. In a thermal relay, the combination with an electromagnetic switchhaving a movable core member, of a normally magnetic-member normallyoperatively engaged by said core member, and means for permitting ofvarying the amount of material of said normally magnetic member.that issubjected to the action of the magnetic lield of said core member andwinding.

4. In a thermal relay, the combinatio with an electromagnetic switchhaving a movable core member, of a normally magnetic current-conductingmember normally operatively engaged by said core member, and adjustablelaterally of said core member to effect a variation in the operationthereof.

5. In a thermal relay, the combination with an electromagnetic switchhaving a movable core member, of a normally magnetic currentconductingmember normally operatively engaged by saidcore member, and means forpermitting of moving said current-conducting member laterally of Saidcoremember to vary the amount of material thereof that is subjected tothe action of the magnetic field of said core member and winding. l

6. An electrical protective device comprisible member, a movablemagnetizable memher differentially associated therewith, and means foraltering the effect of the current on said movable magnetizable member,said magnetically reversible member being rendered nonemagnetic at apredetermined current value.

7. In combination, a coil, a movable core therefor, and acurrent-traversed magnetically reversible member for normally engagingsaid core, said magnetically reversible member having a portion thecurrentconducting area of which varies from one point to another.

8. In combination, a coil, a movable core therefor, and acurrent-traversed magnetically reversible member for normally engagingsaid core, said magnetically reversible member having portions ofminimum and maximum current-conducting areas and an intervening portlonthe current-conducting area of which increases gradually from theportions of minimum area to maximum4 area of which varies from one'pointto an other, and means for adjusting the position of the point ofcontact between said portion and said core.

In testimony whereof, I have hereunto subscribed my name this 21st dayof January, 1925. Y

HAROLD E. WHITE.

